The present invention provides an improved process and apparatus for the injection molding of liquid crystalline polymer. The process produces molded articles having enhanced mechanical properties.
The injection molding of molten thermoplastic polymer is well-known in the art. The conventional method of injection molding is to first inject the polymer melt into the closed mold and, subsequently, to pack additional melt into the cavity to compensate for the densification of the melt during the cooling stage. Conventionally molded articles of liquid crystalline polymer, or other thermoplastics whose mechanical properties are a direct function of their molecular orientation in the molten phase, suffer from low tensile strength in the far or "dead-end" zone of the mold cavity where the melt layers begin to pack. It is in the "dead-end" zone of the mold cavity where the laminar flow of the polymer in the mold cavity strikes the wall of the cavity and reverses its flow direction upon packing. This substantial interruption with laminar flow results in rebound wave patterns on a molecular scale in the melt with concomitant points of structural weakness.
In contrast, the molded articles produced by the apparatus and process of the present invention exhibit enhanced mechanical properties due to the laminar flow orientation of the polymer molecules substantially throughout the molded article.
According to the process of the present invention, articles having improved properties due to the minimization of rebound molecular wave motion (i.e. patterns) within the mold cavity can be formed by allowing the laminar flow of molten polymer to continuously exit through the heretofore dead-end of the injection mold while the mold's cavity is being filled.
Therefore, it is an object of the present invention to provide an improved process for injection molding thermotropic liquid crystalline polymer to form molded articles with enhanced mechanical properties.
It is also an object of the present invention to provide an improved process for injection molding thermotropic liquid crystalline polymer to form molded articles having their constituent polymer molecules oriented in laminar fashion substantially throughout the article.
It is also an object of the present invention to provide an apparatus for the injection molding of thermotropic liquid crystalline polymer to form molded articles with enhanced mechanical properties.
It is also an object of the present invention to provide an apparatus for the injection molding of thermotropic liquid crystalline polymer to form molded articles having their constituent polymer molecules substantially oriented in laminar fashion throughout the article.
It is also an object of the present invention to provide an improved article molded from thermotropic liquid crystalline polymer with enhanced mechanical properties.
It is also an object of the present invention to provide an article molded from thermotropic liquid crystalline polymer wherein the constituent polymer molecules are oriented in laminar fashion substantially throughout the article.